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Astrophysical Spectropolarimetry

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Astrophysical Spectropolarimetry Astrophysical Spectropolarimetry The polarization of light is the key to obtaining a wealth of essential information that lies encoded in the electromagnetic radiation reaching us from cosmic objects. Spectro- polarimetry and imaging polarimetry provide powerful diagnostics of the physical con- ditions in astrophysical plasmas, for instance, concerning magnetic fields, which cannot be obtained via conventional spectroscopy. Spectropolarimetry is being used with great success in solar physics. Yet, its application to other fields of astrophysics is still in an early stage of development. This book on Astrophysical Spectropolarimetry comes at a time of growing awareness of the new possibilities offered by this field. This is mainly due to the observational opportunities opened up by the new generation of telescopes, both ground-based and space-borne, and their associated instrumentation as well as to recent advances in the theory and numerical modelling of the generation and transfer of polarized radiation. The book contains the lectures delivered at the XII Canary Islands Winter School of Astrophysics on the following topics: the physics of polarization, polarized radiation diagnostics of solar magnetic fields, stellar magnetic fields, polarization insights for ac- tive galactic nuclei, compact objects and accretion disks, astronomical masers and their polarization, interstellar magnetic fields and infrared-submillimeter spectropolarimetry, and instrumentation for astrophysical spectropolarimetry. They are written by presti- gious researchers working in several areas of astrophysics, all of them sharing an active interest in theoretical and observational spectropolarimetry. This timely volume provides graduate students and researchers with an unprecedented introduction to Astrophysical Spectropolarimetry. Astrophysical Spectropolarimetry Proceedings of the XII Canary Islands Winter School of Astrophysics Puerto de la Cruz, Tenerife, Spain November 13-24, 2000 Edited by J. TRUJILLO-BUENO Instituto de Astrofisica de Canarias F. MORENO-INSERTIS Instituto de Astrofisica de Canarias F. SANCHEZ Instituto de Astrofisica de Canarias CAMBRIDGE UNIVERSITY PRESS PUBLISHED BY THE PRESS SYNDICATE OP THE UNIVERSITY OF CAMBRIDGE The Pitt Building, Trumpington Street, Cambridge, United Kingdom CAMBRIDGE UNIVERSITY PRESS The Edinburgh Building, Cambridge CB2 2RU, UK 40 West 20th Street, New York, NY 10011-4211, USA 477 Williamstown Road, Port Melbourne, VIC 3207, Australia Ruiz de Alarcon 13, 28014 Madrid, Spain Dock House, The Waterfront, Cape Town 8001, South Africa http://www.cambridge.org © Cambridge University Press 2002 This book is in copyright. Subject to statutory exception and to the provisions of relevant collective licensing agreements, no reproduction of any part may take place without the written permission of Cambridge University Press. First published 2002 Printed in the United Kingdom at the University Press, Cambridge A catalogue record for this book is available from the British Library ISBN 0 521 80998 3 hardback Contents Participants vii Group Photograph ix Preface xi Foreword xiii Acknowledgements xiv The Physics of Polarization E. Landi Degl'Innocenti Introduction 1 Description of polarized radiation 4 Polarization and optical devices: Jones calculus and Mueller matrices .... 7 The Fresnel equations 9 Dichroism and anomalous dispersion 15 Polarization in everyday life 17 Polarization due to radiating charges 20 The linear antenna 23 Thomson scattering 24 Rayleigh scattering 26 A digression on Mie scattering 27 Bremsstrahlung radiation 30 Cyclotron radiation 34 Synchrotron radiation 36 Polarization in spectral lines 38 Density matrix and atomic polarization 39 Radiative transfer and statistical equilibrium equations 44 The amplification condition in polarized radiative transfer 47 Coupling radiative transfer and statistical equilibrium equations 49 References 52 Polarized Radiation Diagnostics of Solar Magnetic Fields J. 0. Stenflo The Sun's magnetic field - An introductory overview 55 Diagnostic techniques - An introductory overview 60 Zeeman-effect diagnostics 68 Hanle diagnostics and coherency effects 83 Extension of the diagnostic range through multi-level effects 91 References 98 Polarized Radiation Diagnostics of Stellar Magnetic Fields G. Mathys General framework 101 Ap stars: an ideal laboratory for stellar magnetic field studies Ill Exploitation of line profile information 121 Magnetic geometries and structures 135 Polarimetric diagnostics of magnetic field in non-Ap stars 141 References 148 v vi Contents Polarization Insights for Active Galactic Nuclei R. Antonucci Seyfert galaxies 151 Radio galaxies 157 Ultraluminous infrared galaxies 161 Emission mechanism for the Big Blue Bump spectral component 166 Conclusions 170 References 170 Compact Objects and Accretion Disks R. Blandford, E. Agol, A. Broderick, J. Heyl, L. Koopmans, H.-W. Lee Disks 177 Jets 186 Outflows 195 Neutron Stars 202 Black Holes 210 References 220 Astronomical Masers and their Polarization M. Elitzur Astronomical masers - Overview 225 Sample maser sources 229 Fundamentals of maser emission 236 Phenomenological maser theory 239 Polarization 247 References 263 Interstellar magnetic fields and infrared-submillimeter spectropolarimetry R. H. Hildebrand Introduction 265 Physical principles of polarized emission 273 The far-infrared polarization spectrum 279 Observing techniques and analysis of results 285 Far-infrared polarimetry in the next ten years 294 References 300 Instrumentation for Astrophysical Spectropolarimetry C. U. Keller Introduction 303 Principles of optical polarization measurements 305 Optical components for spectropolarimetry 312 Instrumental errors 325 Examples of astronomical spectropolarimeters 340 References 352 Participants Ageorges, Nancy European Southern Observatory (Chile) Antonucci, Robert UC Santa Barbara (USA) Aryal, Binil University of Innsbruck (Austria) Asensio, Andres Instituto de Astrofisica de Canarias (Spain) Behlke, Rico Swedish Institute for Space Physics (Sweden) Berdyugina, Svetlana University of Oulu (Finland) Bianda, Michele Istituto Ricerche Solari Locarno (Switzerland) Bland ford, Roger California Institute of Technology (USA) Brogan, Crystal National Radio Astronomy Obs. (USA) Carroll, Thorsten Anthony Astrophysikalisches Institut Postdam (Germany) Collados Vera, Manuel Instituto de Astrofisica de Canarias (Spain) Deetjen, Jochen Int. fur Astronomie und Astrophysik (Germany) Dittinann, Olaf Instituto de Astrofisica de Canarias (Spain) Elitzur, Moshe University of Kentucky (USA) Etoka, Sandra Jodrell Bank Observatory (UK) Feautrier, Nicole Observatoire de Paris (France) Fluri, Dominique ETH Zurich, Institute for Astronomy (Switzerland) Fuhiyoshi, Takuya Cavendish Laboratory (UK) a Galvez Ortiz, M Cruz Universidad Complutense de Madrid (Spain) Gandofer, Achim ETH Zurich, Institute for Astronomy (Switzerland) Garcia Alvarez, David Armagh Observatory (Ireland) Garcia Lorenzo, Begona Isaac Newton Group (Spain) Gisler, Daniel ETH Zurich, Institute for Astronomy (Switzerland) Gonzalez Alfonso, Eduardo I.E.M - CSIC (Spain) Gonzalez Delgado, David Stockholm Observatory (Sweden) Gonzalez Hernandez, Jose J. Universidad de La Laguna (Spain) Gupta, Alok Chandra Physical Research Laboratory (India) Herpin, Fabrice I.E.M - CSIC (Spain) Hildebrand, Robert University of Chicago (USA) Hoffman, Jennifer L. University of Wisconsin-Madison (USA) Holloway, Richard University of Hertfordshire (UK) Ikeda, Yuji University of Tohoku (Japan) Ilyin, Ilya University of Oulu (Finland) Janssen, Katja Georg-August Universitat Gottingen (Germany) Keller, Christoph National Solar Observatory (USA) Kelz, Andreas Astrophysikalisches Institut Postdam (Germany) Khomenko, Elena Main Astronomical Observatory (Ukraine) Kilbinger, Martin Universitate Bonn (Germany) Klement, Joachim ETH Zurich, Institute for Astronomy (Switzerland) Kochukhov, Oleg Uppasala University (Sweden) Kokkonen, Krista K. Tuorla Observatory (Finland) Korhonen, Heidi University of Oulu (Finland) Landi Degl'Innocenti, Egidio Universita di Firenze (Italy) Lopez Santiago, Javier Universidad Complutense de Madrid (Spain) Manso Sainz, Rafael Instituto de Astrofisica de Canarias (Spain) Martin, Fabiola Universidad de La Laguna (Spain) Mathys, Gautier European Southern Observatory (Chile) Modigliani, Andrea European Southern Observatory (Germany) vn Vlll Participants Moreno-Insertis, Fernando Instituto de Astrofisica de Canarias (Spain) Muglach, Karin Astrophysikalisches Institut Postdam (Germany) Miiller, Daniel Kiepenheuer-Institut fiir Sonnenphysik (Germany) Neiner, Coralie Observatoire de Meudon (France) Nielsen, Krister Lund University (Sweden) O'Connor, Padraig National University of Ireland (Ireland) O'Shea, Eoghan ESTEC / Solar System Division (The Netherlands) Packham, Chris University of Florida (USA) Preuss, Oliver Max-Planck-Institut fur Aeronomie (Germany) Romoli, Marco Universita di Firenze (Italy) Sainz Dalda, Alberto THEMIS (Spain) Schlichenmaier, Rolf Kiepenheuer-Institut fiir Sonnenphysik (Germany) Skender, Marina Institute Rudjer Boskovic (Croatia) Stenflo, Jan Olof Institute of Astronomy (Switzerland) Suetterlin, Peter Sterrenkundig Instituut Utrecht (The Netherlands) Telfer, Deborah University of Glasgow (UK) Thum, Clemens IRAM (France) Trujillo-Bueno, Javier Instituto de Astrofisica de Canarias (Spain) Tziotziou, Konstantinos Observatoire de Paris (France) Vlemmings, Wouter Sterrewacht Leiden (The Netherlands) Vogt, Etienne Osservatorio Astronomico di
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